It is already known to glue together sheets of the kind mentioned by manually inserting a first sheet in a gluing machine, and after the gluing operation, during which one side of the sheet is coated with a glue bead along one edge thereof, manually turning the sheet and putting it with the glue side upwards on a base, whereafter a second sheet is manually placed on the base while adjusting this sheet relative the first sheet so that the sheets are caused to overlap each other in the area of the glue bead. The operator subsequently uses his fingers to press the upper sheet against the lower sheet in the area mentioned, whereafter the sheets thus glued together are removed from the base.
A machine is shown and described in the Swedish patent application No. 8303909-9, where sheets of the kind mentioned above are automatically moved from two magazines and automatically moved through the machine while the sheets are aligned at different stations, provided with glue, pressed together and fed out from the machine.
The sheets now glued together are inserted in a machine, e.g. of the kind illustrated in the U.S. Pat. No. 4,376,061, for providing the part of the one sheet, which is to form the spine of the finished folder or file, with a hot-melt glue bead and also to achieve crease lines between the spine and covers. After the covers have been folded along the crease lines so that they lie opposite each other, sheets of paper can be inserted between the covers and be caused to engage against the hot-melt glue bead on the inside of the spine, and the folder or file is placed on a heated base in an apparatus, e.g. of the kind illustrated in the U.S. Pat. No. 4,367,116, so that this bead melts and the edges of the sheet adhere to the inside of the spine.
Manual handling of both sheets in conjunction with gluing the latter is very time-consuming. Furthermore, the manual handling results in a relatively poor product with regard to quality, since the alignment of the sheets relative each other in the gluing area cannot be made exactly, and since the compressive force in this area varies along the length of the bead.
The fully automatic handling of both sheets in conjunction with gluing is rapid, but requires a complicated and expensive machine. Furthermore, the risk of operational disturbances is large. It has also been found that the alignment of the sheets during the different operations will bot be exact, and that the aligning means must be reset for producing differently sized folders.